Load levelling batteries

Load levelling batteries 5-100 MWh Spinning reserve, peak shaving, load levelling... 

Fig. 1.7 Artist s impression of a 100 MWh load levelling battery. (By courtesy of I.D.C. Cargill, University of St Andrews.)...

R. G. Zalosh and S. N. Bajpai, Comparative Hazard Investigation for a Zinc-Bromine Load-Leveling Battery, Factory Mutual Research Corp. for Electric Power Research Institute, Project... 

At Yuasa Battery Co. in Japan, a 50-kW, 400-kW h Na-S load-leveling battery has been constructed, and it has demorrstrated an energy efficiency of 85% for cycle of 8 h charge and 8 h discharge, and a 48.5-kW h m" energy-area ratio. Test of a 10-kW Na-S battery has started in 1992 at Hitachi Works. The battery is consists of 192 cells of 252 Ah capacity each. This battery can operate at a cmrent of 345 A and delivers an energy density of 60 Whkg-. ... 

Dow Chemical Co. has mamrfactuied a Na-S-glass battery in which the electrolyte is a Na+-borate glass formed by fibers. Cycle lives exceeding 500 cycles at 8% discharge have been obtained for individual cells, and a load-leveling battery has been designed which will use 12,500 gas-cooled cells of 0.8-kW h capacity. 

In the 1990s, the use of batteries in electric vehicles and for load leveling is being revived partly for environmental reasons and partly because of scarce energy resources. Improvements in battery performance and life, fewer maintenance requirements, and automatic control systems are making these appHcations feasible. Research and development is ongoing all over the world to develop improved lead—acid batteries as weU as other systems to meet these needs. 

Redox flow batteries, under development since the early 1970s, are stUl of interest primarily for utility load leveling applications (77). Such a battery is shown schematically in Figure 5. Unlike other batteries, the active materials are not contained within the battery itself but are stored in separate tanks. The reactants each flow into a half-ceU separated one from the other by a selective membrane. An oxidation and reduction electrochemical reaction occurs in each half-ceU to generate current. Examples of this technology include the iron—chromium, Fe—Cr, battery (79) and the vanadium redox cell (80). 

Other flow batteries investigated for both electric vehicle appHcation and utiUty load leveling include 2inc [7440-66-6]—[7782-50-5] Zn—Q.25 and zinc—bromine [7726-95-6]., Zn—Br2, batteries (78,81,82). 

Zinc—bromine storage batteries (qv) are under development as load-leveling devices in electric utilities (64). Photovoltaic batteries have been made of selenium or boron doped with bromine. Graphite fibers and certain polymers can be made electrically conductive by being doped with bromine. Bromine is used in quartz—haUde light bulbs. Bromine is used to etch aluminum, copper, and semi-conductors. Bromine and its salts are known to recover gold and other precious metals from their ores. Bromine can be used to desulfurize fine coal (see Coal conversion processes). Table 5 shows estimates of the primary uses of bromine. 

While the zinc/chlorine battery is preferred for utility load-leveling applications [49], the zinc/bromine system is the more promising one for electric vehicle requirements [50, 51]. 

Recently the development of Na/S batteries for car applications has been abandoned only Na/S batteries for stationary applications (load leveling) are still under development in Japan. Among the high-temperature batteries, the ZEBRA battery is the only system at present which is being commercialized for car applications. 

Nonwoven materials such as cellulosic fibers have never been successfully used in lithium batteries. This lack of interest is related to the hygroscopic nature of cellulosic papers and films, their tendency to degrade in contact with lithium metal, and their susceptibility to pinhole formation at thickness of less than 100 fjim. For future applications, such as electric vehicles and load leveling systems at electric power plants, cellulosic separators may find a place because of their stability at higher temperatures when compared to polyolefins. They may be laminated with polyolefin separators to provide high-temperature melt integrity. 

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